No brake lights but switch works

[rockusaf]

I have a lot going on with my truck right now with an LS3/Tremec 6 speed swap and 1998 dash install (truck is a 1991), making progress but I need some help with the brake lights. I pulled the mount and brake pedal with the dash and put in a new brake light switch but got no brake lights when I push the pedal (turn signals, parking lights and hazards work).

If I reach under the dash and push on the switch towards where the stud from the pedal goes through it the lights will come on so I know everything is wired up correctly and the switch itself is working but I can't figure out how the switch works normally. Looking at the switch I can see the metal piece offset in the hole and understand how it's supposed to be pushed back to turn the lights on but don't get how that happens when it's mounted in the truck, can anyone explain how the switch doesn't just move with the rod it's clipped on and how it's activated?

Am I missing something other than the rod going to the brake booster, the switch and the clip that holds the switch on there? I still have the 1991 brake booster but from what I can see there's no difference in the rods for a 1998, could this be the problem? I can't get the truck on the road without brakes so any ideas are appreciated.

Thanks,
Rock

 

[beardeddummy]

You need a shim to help the rod activate the switch it's weird but I've seen it before

 

[rockusaf]

You need a shim to help the rod activate the switch it's weird but I've seen it before

Can you give me any specifics on this? I'm not sure how it would work and still allow you to remove the rod from the brake booster if need be later on.

Thanks,
Rock

 

[beardeddummy]

I used a piece of metal like from a metal stud inside the switch where the rod for the brake petal. Maybe some piece of exhaust strapping just to take up the slack in the switch. If all that makes sense

 

[rockusaf]

I used a piece of metal like from a metal stud inside the switch where the rod for the brake petal. Maybe some piece of exhaust strapping just to take up the slack in the switch. If all that makes sense

Well I've done a bunch of searching and not finding much, pulled the brake switch off to see how far that metal lever needed to move and it's got to be pushed quite a bit to work, just about all the way to even with the plastic housing. If I stick a screwdriver in the hole and push on the lever the brake lights come on so I know everything from the switch back works as designed. It's just the interface between the stud on the brake pedal and this switch.

Beardeddummy, are you talking about basically putting a piece of metal around the stud, essentially making the diameter of the stud bigger? That should be easy enough to try but not sure how that will activate the switch since the hole is oblong as you can sort of see in the below pic, so that stud needs to move while that switch stays put on the rod and maybe I'm just dense but I really don't see how that happens.

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One thing I did notice is that I've got the clips like the bottom right of the above pic but all the videos I found explaining replacing the switch have the clips like the ones at the top, could these be part of the problem? I'll probably pick some up since they're cheap enough but not hopeful they'll make much of a difference.

Rock

 

[someotherguy]

The new style switch hit the scene in 1994 and used the semi-rectangular clip at first. 1995 or maybe 1996 they switched to the round clip. I don't think there's any functional difference, it's just a clip; dunno why they changed it. (I'll throw in a guess - the round clip is probably far easier on assembly line installation)

It's probably a long shot but are you 100% sure your brake pedal pushrod isn't bent at all? This crops up every now and then on GMT400's that have been severely panic-stopped in the past. While it wouldn't have been as big a deal with the 88-93 style brake switch because those are adjustable, the 94-up switch being non-adjustable could present a problem.

Also did you use a brand new brake switch or a used one? They are known for going bad but the usual failure mode is the leafs inside break off from too many cycles, however they also bend a little bit out of whack before they break...causing the need for more pedal travel before they make contact.

Richard

 

[rockusaf]

Thanks for the info Richard, I thought the clip was a long shot but I'm grasping at straws at this point. I went out to the garage and looked, the rod looks straight and I've got the steering column dropped so I can get a really good look at everything and make it easier to work in there.

The switch is brand new and right now I've got it removed and I gave it a good look over and it doesn't look like anything is tweaked or cracked. It all works when I push the little metal lever the lights come on and it springs back to turn them off so it seems like the switch is fine.

This doesn't seem that complicated that's why I'm just like

Rock

 

[Pip7899]

Check the harness by the left foot well on the drivers side wiggle those wires while you push the brake . Switch may be perfectly fine. That pass through connector gets loose.

 

[beardeddummy]

Your on the right path with the shim try sticking a dime in their you don't have to go around the rod just something in between the rod and switch.

 

[98xcab3/4sbed]

My truck is having a problem kind of like this. Switch works. I replaced it with an AutoZone part and it did the same thing. Than replaced with a gm one and the same thing. Mine had the lights come on with a little push of the brake peddle then go off after a little more and then come back on when it is pushed all the way down. I think I got it figured out. Seems like someone wired in the trailer brake controller into the light circuit. Just used a crimp conector and it's not a good connection. I jiggle it a bit and it gets better. Hope this helps you out.